As manufacturing techniques for ULSI semiconductor elements, processing techniques for densification and miniaturization of the semiconductor elements have been presently researched and developed. A CMP (Chemical Mechanical Polishing) technique is one of such processing techniques. A flattening technique using CMP has become an essential technique for flattening interlayer insulating materials, forming STI (Shallow Trench Isolation), forming plugs, forming embedded metal wires (damascene step) and the like, in manufacturing steps of semiconductor elements. Generally, a CMP step (a flattening step using a CMP technique) is performed by supplying a polishing liquid for CMP between a polishing pad (polishing cloth) and a material to be polished of a base and by polishing the material to be polished with the polishing pad.
Various polishing liquids have been known as the polishing liquid for CMP used for CMP. When the polishing liquid for CMP is classified according to the kinds of abrasive grains (polishing particles), a ceria-based polishing liquid comprising cerium oxide (ceria) particles, a silica-based polishing liquid comprising silicon oxide (silica) particles, an alumina-based polishing liquid comprising aluminum oxide (alumina) particles, and a resin particle-based polishing liquid comprising organic resin particles, or the like have been known.
Incidentally, in recent years, achievement of further miniaturization of wires has been required in manufacturing steps of semiconductor elements, and polishing scratches generated during polishing have become a problem. Specifically, when polishing is performed using conventional polishing liquids, generation of fine polishing scratches gives no problem as long as the size of the polishing scratches is smaller than the conventional wire width, but becomes a problem in the case where further miniaturization of wires is tried to be achieved.
For this problem, the average particle diameter of abrasive grains comprised in the polishing liquid is tried to be reduced. However, if the average particle diameter is reduced, the polishing rate may be decreased due to a decrease in the mechanical action. In this way, both a polishing rate and polishing scratches are extremely difficult to be achieved. In response to this, polishing liquids using abrasive grains including a hydroxide of a tetravalent metal element have been studied (for example, refer to the following Patent Literature 1 to 4).